For fans of casual games (those small games you play on a smartphone or tablet while you’re waiting for a train) this was a big week. Electronic Arts just released Plants Vs. Zombies 2 for the iOS platform. The original is a favorite of mine that I still play, even though I’ve completed the game a few times.

The sequel is in many ways better than the original, with new worlds to explore (there’s a time travel theme to this one), new zombies to conquer, and of course new plants. Plants are weapons in this cartoony game, so you use peashooters, cabbage-pults, and bloomerangs to dispatch your enemies.

While the casual gaming world should be thrilled to get such a great new game, the talk has instead been about the heavy use of in-app purchases (IAP). Electronic Arts has chosen to go with the “freemium” model for this game, meaning Plants Vs. Zombies 2 is free, but the game charges for extras such as new plants, worlds, and powers.

The increase in IAP has been a controversial area. Apple recently cracked down on children’s games that use it, now requiring a parental password for any in-app purchases.

For adult gamers, we’ll have to watch our wallets. While some of us are tightwads and would never spend a dime on extras, many gamers pay plenty. Analyst firm Distimo just published a report showing that 71 percent of all iPhone app revenue comes from in-app purchases in free games.

For cheapskates, IAP is both good and bad: While I like that IAP games are typically free, I hate the constant in-game messages to pay for extras. I’d rather pay $3 or $4 for a complete game with no extras to buy than download a free game with constant ads. But with IAP pulling in big revenue for game developers, I don’t see the system changing anytime soon.

Follow TROY DREIER at http://twitter.com/TDreier or e-mail him at loggedon@mac.com.